CBSE 2022 · Region 3 · Set 1 · Q2 · 2 marks
(i)Distinguish between isotopes and isobars.(ii)Two nuclei have different mass numbers $\displaystyle \mathrm{A}_{1}$ and $\displaystyle \mathrm{A}_{2}$. Are these nuclei necessarily the isotopes of the same element ? Explain.(i)Name the factors on which photoelectric emission from a surface depends.(ii)Define the term 'threshold frequency' for a photosensitive material.
(i)
Distinguish between isotopes and isobars.
(ii)
Two nuclei have different mass numbers $\displaystyle \mathrm{A}_{1}$ and $\displaystyle \mathrm{A}_{2}$. Are these nuclei necessarily the isotopes of the same element ? Explain.
(i)
Name the factors on which photoelectric emission from a surface depends.
(ii)
Define the term 'threshold frequency' for a photosensitive material.
Marking-scheme solution
(i) Isotopes - These are the atoms having same atomic number (Z) but different atomic mass(A).
Isobars - The atoms of different element having same atomic masses.
(ii) No the mass number of a nucleus is the sum of number of proton(Z) and number of neutrons (N) / $\displaystyle A=Z+N /$ Two nuclei with different mass numbers $\displaystyle \mathrm{A}_{1}$ and $\displaystyle \mathrm{A}_{2}$, may have, have different $\displaystyle Z$.
OR
(i) Factors
(a) Frequency of incident radiation
(b) Work function of the surface
(ii) The minimum frequency of the incident radiation below which photoelectric emission does not take place.
NucleiAtomic Masses and Composition of NucleusUnderstandvery_short_answereasy
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CBSE Class 12 Physics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.